1. Field of the Invention
The present invention relates to a transmission for automotive vehicles and refers more particularly to a transmission unit comprising a variator and differential group used in combination with an internal combustion engine. The axis common to the engine and the primary shaft of the variator as well as the axis of its secondary shaft are most often arranged transversally to the longitudinal axis of the vehicle.
2. Description of the Prior Art
Although numerous improvements have been made on this type of transmission, it still presents drawbacks with respect to energy economy. For reasons of space, cost and efficiency, variators usually have a range of ratios in the order of 4 or 5, while the range of ratios should be in the order of 6 to 8. Indeed, such an expanded range of ratios permits more efficient operation of most of the internal combustion engines used in automotive vehicles.
Also, efforts to improve the belt's resistance to wear cause a certain amount of over-dimensioning aimed at reducing the frequency of replacement and, on the other hand, the overall efficiency of the variator is not always satisfactory.